U.S. patent application number 14/347164 was filed with the patent office on 2014-08-21 for motor.
The applicant listed for this patent is ASMO CO., LTD.. Invention is credited to Tetsuya Honda.
Application Number | 20140232247 14/347164 |
Document ID | / |
Family ID | 47995474 |
Filed Date | 2014-08-21 |
United States Patent
Application |
20140232247 |
Kind Code |
A1 |
Honda; Tetsuya |
August 21, 2014 |
MOTOR
Abstract
A coupling portion is provided on either a rotary shaft or a
worm shaft in an integrally rotational manner, said coupling
portion for connecting the rotary shaft to the worm shaft and
having a coupling hole therein. The coupling projection provided on
the other of the rotary shaft and the worm shaft is inserted in the
coupling hole. A circumferential clearance and a radial clearance
are formed between the inner surface of the coupling hole and the
coupling projection. Circumferential buffer portions are interposed
in the circumferential clearance, and radial buffer portions are
interposed in the radial clearance. The inner surface of the
coupling hole and the coupling projection are arranged such that
the circumferential buffer portions are compressed to deform in the
circumferential direction whereby to allow the buffer portions to
be brought into contact with each other when the rotary shaft is
rotating.
Inventors: |
Honda; Tetsuya; (Kosai-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ASMO CO., LTD. |
Shizuoka-ken |
|
JP |
|
|
Family ID: |
47995474 |
Appl. No.: |
14/347164 |
Filed: |
September 24, 2012 |
PCT Filed: |
September 24, 2012 |
PCT NO: |
PCT/JP2012/074404 |
371 Date: |
March 25, 2014 |
Current U.S.
Class: |
310/75D |
Current CPC
Class: |
H02K 7/003 20130101;
H02K 7/1166 20130101; H02K 7/118 20130101 |
Class at
Publication: |
310/75.D |
International
Class: |
H02K 7/00 20060101
H02K007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 30, 2011 |
JP |
2011-217245 |
Claims
1. A motor comprising: a motor body having a rotary shaft; a speed
reduction mechanism, which includes a worm shaft and a worm wheel
meshed with the worm shaft; and a coupling portion, which has a
coupling hole and couples the rotary shaft and the worm shaft with
each other so that the rotary shaft the worm shaft are integrally
rotational, wherein the coupling portion is provided to be
rotational integrally with one of the rotary shaft and the worm
shaft, a coupling projection is provided on the other one of the
rotary shaft and the worm shaft, the coupling projection being
inserted in the coupling hole, a circumferential clearance, which
is a clearance in a circumferential direction, and a radial
clearance, which is a clearance in a radial direction, are formed
between an inner surface of the coupling hole and the coupling
projection, a circumferential buffer portion is located in the
circumferential clearance, a radial buffer portion is located in
the radial clearance, and the inner surface of the coupling hole
and the coupling projection are configured to be contactable with
each other in the circumferential direction while compressing and
deforming the circumferential buffer portion in the circumferential
direction when the motor body is driven to rotate the rotary
shaft.
2. The motor according to claim 1, wherein the rotary shaft and the
worm shaft are made of metal, and the coupling portion is a plastic
member formed separately from the rotary shaft and the worm
shaft.
3. The motor according to claim 2, wherein the circumferential
buffer portion and the radial buffer portion are provided in the
coupling portion.
4. The motor according to any claim 1, wherein the circumferential
buffer portion and the radial buffer portion are made of
rubber.
5. The motor according to claim 1, wherein an axial buffer portion
is located between the coupling projection and a bottom surface of
the coupling hole in the axial direction.
6. The motor according to claim 5, wherein the rotary shaft and the
worm shaft are made of metal, the coupling portion is a plastic
member formed separately from the rotary shaft and the worm shaft,
and the axial buffer portion is provided in the coupling
portion.
7. The motor according to claim 5, wherein the axial buffer portion
is made of rubber.
8. The motor according to claim 1, wherein the inner surface of the
coupling portion has a contact portion that contacts the coupling
projection, and the circumferential buffer portion is located
radially inward of the contact portion of the coupling hole inner
surface.
Description
RELATED APPLICATIONS
[0001] The present is a National Phase entry of PCT Application No.
PCT/JP2012/074404, filed Sep. 24, 2012, which claims priority from
Japanese Patent Application No. 2011-217245, filed Sep. 30, 2011,
the disclosures of which are hereby incorporated by reference
herein in their entirety.
FIELD OF THE INVENTION
[0002] The present disclosure relates to a motor having a speed
reduction mechanism that includes a worm shaft and a worm
wheel.
BACKGROUND OF THE INVENTION
[0003] Conventionally, this type of motor includes a worm shaft,
which is coaxially coupled to a rotary shaft, or a drive shaft, of
a motor body to rotate integrally with the drive shaft. For
example, a motor disclosed in Japanese Laid-Open Patent Publication
No. 2009-11077 includes a rotary shaft and a worm shaft, which are
made of metal. The worm shaft includes a coupling portion formed at
an axial end. A coupling hole is formed in the coupling portion. A
coupling projection at a distal end of the rotary shaft is inserted
into the coupling hole, so that the rotary shaft and the worm shaft
are directly coupled to each other.
[0004] In the above described motor, for example, when the rotary
shaft and the speed reduction mechanism are driven to rotate in the
forward direction, the load from the output portion may stop, or
locks, the rotation. At this time, the teeth of the worm shaft, or
the worm portion, may bind with the teeth of the worm wheel. If the
rotary shaft and the speed reduction mechanism begin rotating in
the reverse direction from this state, torque for undoing the bound
state is required in addition to the torque for rotating the worm
shaft.
[0005] To solve this problem, clearances may be provided between
the inner surface of the coupling hole of the worm shaft and the
coupling projection of the rotary shaft both in the circumferential
direction and in the radial direction. In a case in which such
clearances are provided, when the rotary shaft starts rotating in
the reverse direction from the bound state, that is, when the
rotary shaft starts rotating in the reverse direction, the rotary
shaft is rotated freely for a certain period of time. In this
period, the rotary shaft gains an inertial force, or a rotational
momentum. After rotating freely due to the clearances, the rotary
shaft violently strikes the inner surface of the worm shaft
coupling hole with the inertial force. This releases the bound
teeth of the worm shaft and the worm wheel from each other in a
favorable manner.
SUMMARY OF THE INVENTION
Problems that the Invention is to Solve
[0006] In the above described motor, the clearances in the
circumferential direction and the radial direction are formed
between the inner surface of the worm shaft coupling hole and the
rotary shaft coupling projection. Therefore, when the above
described motor is operating, for example, the worm shaft may move
uncontrollably in the circumferential direction and the radial
direction due to, for example, imperfect alignment. Uncontrollable
movements of the worm shaft may cause the inner surface of the
coupling hole to strike the coupling projection, resulting in
noises.
[0007] Accordingly, it is an objective of the present disclosure to
provide a motor that suppresses the generation of noises caused by
uncontrollable movements of a worm shaft.
Means for Solving the Problems
[0008] In accordance with one aspect of the present disclosure, a
motor is provided that includes a motor body having a rotary shaft,
a speed reduction mechanism, which includes a worm shaft and a worm
wheel meshed with the worm shaft, and a coupling portion, which has
a coupling hole and couples the rotary shaft and the worm shaft
with each other so that the rotary shaft the worm shaft are
integrally rotational. The coupling portion is provided to be
rotational integrally with one of the rotary shaft and the worm
shaft. A coupling projection is provided on the other one of the
rotary shaft and the worm shaft. The coupling projection is
inserted in the coupling hole. A circumferential clearance, which
is a clearance in a circumferential direction, and a radial
clearance, which is a clearance in a radial direction, are formed
between an inner surface of the coupling hole and the coupling
projection. A circumferential buffer portion is located in the
circumferential clearance. A radial buffer portion is located in
the radial clearance. The inner surface of the coupling hole and
the coupling projection are configured to be contactable with each
other in the circumferential direction while compressing and
deforming the circumferential buffer portion in the circumferential
direction when the motor body is driven to rotate the rotary
shaft.
[0009] According to this configuration, the circumferential buffer
portion and the radial buffer portion are provided in the
circumferential clearance and the radial clearance between the
inner surface of the coupling hole and the coupling projection,
respectively. This reduces uncontrollable movements of the worm
shaft when rotating. As a result, the generation of noise caused by
the coupling hole inner surface striking the coupling projection is
suppressed. Further, when the rotary shaft is driven to rotate in
the reverse direction, that is, when the rotary shaft starts
rotating in the reverse direction with the worm shaft bound with
the worm wheel, the rotary shaft rotates while compressing and
deforming the circumferential buffer portion between the coupling
hole inner surface and the coupling projection. During this time,
the rotary shaft gains inertial force, or the momentum of rotation.
Thereafter, with the circumferential buffer portion compressed, the
coupling hole inner surface and the coupling projection contact
each other in the circumferential direction while receiving the
inertial force of the rotary shaft. This releases the worm shaft
and the worm wheel, which have been bound to each other, from each
other. According to this configuration, as described above, the
circumferential buffer portion and the radial buffer portion
suppress uncontrollable movements of the worm shaft, while ensuring
the inertial force of the rotary shaft using the clearance between
the coupling projection and the inner surface of the coupling
hole.
[0010] According one form of the disclosure, the rotary shaft and
the worm shaft are made of metal, and the coupling portion is a
plastic member formed separately from the rotary shaft and the worm
shaft.
[0011] According to this configuration, the inner surface of the
coupling hole, into which the coupling projection of the worm shaft
or the rotary shaft is inserted, is also made of plastic. Thus,
when the motor body rotates the rotary shaft, noise caused by the
coupling hole inner surface striking the coupling projection in the
circumferential direction is suppressed. This further suppresses
the generation of noise.
[0012] According one form of the disclosure, the circumferential
buffer portion and the radial buffer portion are provided in the
coupling portion.
[0013] According to this configuration, the circumferential buffer
portion and the radial buffer portion are formed in the coupling
member, which is a plastic member separate from the rotary shaft
and the worm shaft. The circumferential buffer portion and the
radial buffer portion can therefore be formed.
[0014] According one form of the disclosure, the circumferential
buffer portion and the radial buffer portion are made of
rubber.
[0015] According to this configuration, since the circumferential
buffer portion and the radial buffer portion are made of rubber,
uncontrollable movements of the worm shaft are suppressed in a
favorable manner.
[0016] According one form of the disclosure, an axial buffer
portion is located between the coupling projection and a bottom
surface of the coupling hole in the axial direction.
[0017] According to this configuration, due to the characteristics
of the worm shaft and the worm wheel of the speed reduction
mechanism, reversal of rotation of the worm shaft generates a load
in the axial direction. The load may cause the coupling projection
to strike the bottom surface of the coupling hole in the axial
direction or may cause the worm shaft to strike the rotary shaft in
the axial direction. However, such possible striking is suppressed
by the axial buffer portion. As a result, the generation of noise
caused by such striking is suppressed.
[0018] According one form of the disclosure, the rotary shaft and
the worm shaft are made of metal. The coupling portion is a plastic
member formed separately from the rotary shaft and the worm shaft,
and the axial buffer portion is provided in the coupling
portion.
[0019] According to this configuration, the axial buffer portion is
formed in the coupling member, which is a plastic member separate
from the rotary shaft and the worm shaft. The axial buffer portion
can therefore be formed easily.
[0020] According one form of the disclosure, the axial buffer
portion is made of rubber.
[0021] According to this configuration, since the axial buffer
portion is made of rubber, the coupling projection is prevented
from striking the bottom surface of the coupling hole in the axial
direction, and the worm shaft is prevented from striking the rotary
shaft in the axial direction in a favorable manner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a cross-sectional view of a motor;
[0023] FIG. 2A is a plan view of a joint as viewed from a worm
shaft;
[0024] FIG. 2B is a cross-sectional view of the joint; and
[0025] FIG. 3 is an explanatory plan view of operation of the
motor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] Hereinafter, a preferred embodiment according to the present
disclosure will be described.
[0027] A motor 1 illustrated in FIG. 1 is used, for example, as a
drive source of a wiper device (not shown) mounted on a vehicle.
The motor 1 includes a motor body 2 and a speed reducing portion 3,
which reduces the speed and increases the torque of the output
rotation of the motor body 2 and transmits the rotation to the
wiper device.
[0028] The motor body 2 also includes a yoke 4 as a yoke housing.
The yoke 4 is made of conductive metal and shaped as a cylinder
with a closed end. A flange 4b is formed at an opening 4a of the
yoke 4. The speed reducing portion 3 has a housing 6. The flange 4b
is coupled and fixed to a fixing portion 6a of the gear housing 6
with bolts B.
[0029] A brush holder 5, which is made of an insulating material
such as plastic, is attached to the opening 4a of the yoke 4 to
close the opening 4a. When the yoke 4 and the gear housing 6 are
secured to each other with the bolts B, the brush holder 5 is
tightly held by the flange 4b and the fixing portion 6a of the gear
housing 6.
[0030] Magnets MG are fixed to the inner surface of the yoke 4 to
face each other. An armature (rotor) 7 is rotationally accommodated
inward of the magnets MG which face each other. A rotary shaft 8 is
fixed to the armature 7. The proximal end of the rotary shaft 8 is
rotationally supported by a bearing 9a provided on the inner bottom
of the yoke 4. A bearing 9b is attached to a center position of the
brush holder 5 to rotationally support the distal end of the rotary
shaft 8, which protrudes into the gear housing 6.
[0031] The brush holder 5 holds a pair of feeder brushes 5a. The
brushes 5a are configured to slide along segments SG of a
commutator 7a of the armature 7 to feed currents to the segments
SG. The brush holder 5 has a connector portion 5b, which is
connectable with an external connector (not shown). Currents from
the external connector are supplied to the brushes 5a via terminals
5c provided in the connector portion 5b.
[0032] The speed reducing portion 3 includes the gear housing 6 and
a speed reduction mechanism 11 accommodated in the gear housing 6.
A joint accommodating portion 12 is formed in the gear housing 6 at
the fixing portion 6a, which is fixed to the yoke 4. The joint
accommodating portion 12 has an opening that faces the yoke 4. The
gear housing 6 has a worm shaft accommodating portion 13 and a worm
wheel accommodating portion 14. The worm shaft accommodating
portion 13 extends from the joint accommodating portion 12 along an
axis L1 of the rotary shaft 8 and in a direction opposite from the
yoke 4. The worm wheel accommodating portion 14 is located beside
the worm shaft accommodating portion 13, or on the lower side as
viewed in FIG. 1.
[0033] The rotary shaft 8 extends through the brush holder 5 and
has a distal end 8a, which protrudes into the joint accommodating
portion 12. The joint accommodating portion 12 accommodates a joint
16 in it. The joint 16 is a coupling portion that couples the
distal end 8a of the rotary shaft 8 and a worm shaft 15
accommodated in the worm shaft accommodating portion 13 to each
other.
[0034] The worm shaft 15 is arranged to be coaxial with the rotary
shaft 8. The worm shaft 15 has a proximal end, which is located at
the right end as viewed in FIG. 1 and is connected to the joint 16.
At the proximal end, that is, in the vicinity of a coupling
projection 15a, which will be discussed below, the worm shaft 15 is
rotationally supported by a bearing 17a provided in the gear
housing 6. The distal end of the worm shaft 15 is rotationally
supported by a bearing 17b provided in the worm shaft accommodating
portion 13. The worm shaft 15 has a screw-like worm portion 15b
formed at center portion in the axial direction, or a section
between the bearings 17a, 17b. The worm shaft accommodating portion
13 has a thrust receiving plate 17c at a closed end in the axial
direction. The thrust receiving plate 17c receives thrust load of
the worm shaft 15.
[0035] The internal space of the worm shaft accommodating portion
13 is connected to the internal space of the worm wheel
accommodating portion 14. The worm wheel accommodating portion 14
rotationally accommodates a disk-like worm wheel 18 in it. The worm
wheel 18 is meshed with the worm portion 15b. The axis of the worm
wheel 18 extends perpendicular to the axis of the worm shaft 15, or
in a direction perpendicular to the sheet of FIG. 1. The worm wheel
18 and the worm shaft 15 form the speed reduction mechanism 11. An
output shaft 19 is provided at the radial center of the worm wheel
18 to be rotational integrally with the output shaft 19 so that the
output shaft 19 extends along the axis of the worm wheel 18. The
output shaft 19 has a distal end, which is coupled to the wiper
device.
[Structure of Joint]
[0036] Hereinafter, the joint 16, which couples the rotary shaft 8
of the motor body 2 and the worm shaft 15 of the speed reducing
portion 3 to each other, will be described with reference to FIGS.
2A and 2B. As shown in FIG. 2B, the joint 16 has a plastic portion
20, which is fixed to the distal end 8a of the rotary shaft 8 to
rotate integrally with the rotary shaft 8, first rubber members 21,
and second rubber members 22a, 22b. The first and second rubber
members 21, 22a, 22b are integrally formed with the plastic portion
20 by two-color molding.
[0037] The plastic portion 20 has a substantially cylindrical
fixing portion 23, which is fixed to the distal end 8a of the
rotary shaft 8. The distal end 8a of the rotary shaft 8 has a flat
shape with a pair of parallel surfaces. The distal end 8a is
press-fitted in a press-fitting hole 24, which is formed to extend
axially through a center portion of the fixing portion 23.
[0038] The fixing portion 23 has a pair of rubber accommodating
holes 25 located about, or radially outside of, the press-fitting
hole 24. The rubber accommodating holes 25 are arranged at a
180-degree interval in the circumferential direction. Each rubber
accommodating hole 25 has one of the first rubber members 21. An
end of each first rubber member 21 that is closer to the worm shaft
15 serves as a projection 21a, which protrudes in the axial
direction from an end face 23a of the fixing portion 23 that is
close to the worm shaft 15. The end face 23a is a bottom surface of
coupling hole 28 in the axial direction. The first rubber members
21 are axial buffer portions, which absorb the load in the axial
direction received by the worm shaft 15 toward the motor body 2.
Each first rubber member 21 has at its ends in the axial direction
a step portion 21b. The step portions 21b are engaged with the
rubber accommodating hole 25 in the axial direction to prevent the
first rubber member 21 from coming off in the axial direction.
[0039] A worm shaft coupling portion 26 is integrally formed in a
part of the fixing portion 23 that is close to the worm shaft 15.
The worm shaft coupling portion 26 has a cylindrical shape with a
diameter larger than the fixing portion 23. That is, in the present
embodiment, the plastic portion 20 as a small diameter portion and
the worm shaft coupling portion 26 as a large diameter portion form
a plastic single member extending along the axis L1. A flange
portion 27 is formed at an axial end of the worm shaft coupling
portion 26 that is close to the motor body 2.
[0040] As shown in FIG. 2A, a coupling hole 28 is formed in a
center portion of the worm shaft coupling portion 26. The coupling
hole 28 receives the coupling projection 15a, which is formed at
the proximal end of the worm shaft 15. The coupling projection 15a
of the worm shaft 15 has a flat shape with parallel flat surfaces
15x, 15y, which extend along the axis L1. The coupling projection
15a is formed to be symmetrical about the axis L1. The coupling
projection 15a has longitudinal-direction end faces 15c, 15d, which
bulge radially outward and are located between the flat surfaces
15x and 15y. In contrast, the inner surface of the coupling hole 28
of the worm shaft coupling portion 26 has an elongated shape
slightly larger than the shape of the coupling projection 15a when
viewed in the axial direction. That is, the inner surface of the
coupling hole 28 has a flattened shape and symmetrical about the
axis L1. Clearances C1, C2 are formed between the inner surface of
the coupling hole 28 and the coupling projection 15a. Specifically,
circumferential clearances C1 are formed between the inner surface
of the coupling hole 28 and the flat surfaces 15x, 15y, while
radial clearances C2 are formed between the inner surface of the
coupling hole 28 and the longitudinal-direction end faces 15c, 15d
at the longitudinal-direction ends of the coupling projection 15a.
The worm shaft coupling portion 26 has the second rubber members
22a, 22b, which are embedded by two-color molding. Each of the
second rubber members 22a, 22b is formed by a circumferential
buffer portion 31, a radial buffer portion 32, and a coupling
portion 33, which couples the buffer portions 31, 32 to each other.
The second rubber members 22a, 22b are formed symmetrically with
respect to the axis L1.
[0041] The circumferential buffer portion 31 of each of the second
rubber members 22a, 22b has a recess 28a, which is formed by
radially outwardly recessing the inner surface of the coupling hole
28. The inner surface of the coupling hole 28 includes contact
portion 28b, 28e on both sides of the circumferential buffer
portion 31 of the second rubber member 22a, and contact portions
28d, 28c on both sides of the circumferential buffer portion 31 of
the second rubber member 22b. The contact portion 28b and the
contact portion 28c are symmetrical about the axis L1, and the
contact portion 28d and the contact portion 28e are symmetrical
about the axis L1. A part of the circumferential buffer portion 31
protrudes radially inward from the recess 28a. In the state
illustrated in FIG. 2A, if the motor 1 is not operating, the
circumferential buffer portions 31 of the second rubber members
22a, 22b contact the flat surfaces 15x, 15y of the coupling
projection 15a at two positions that are symmetrical about the axis
L1 of the worm shaft 15. That is, in FIG. 2A, the circumferential
buffer portion 31 of the left-hand second rubber member 22a
contacts the flat surface 15x at two positions with the axis L1 in
between, and the right-hand second rubber member 22b contacts the
flat surface 15y at two positions with the axis L1 in between. The
two positions at which one of the circumferential buffer portions
31 contacts the flat surface 15x and the two positions at which the
other circumferential buffer portion 31 contacts the flat surface
15y are symmetrical about the axis L1.
[0042] The radial buffer portions 32 of the second rubber members
22a, 22b project radially inward from the inner surface of the
coupling hole 28 and contact the longitudinal-direction end faces
15c, 15d of the coupling projection 15a. A contact surface 32a of
each radial buffer portion 32 contacts the coupling projection 15a
and projects arcuately radially inward. As described above, in a
direction perpendicular to the axis, that is, in the plane of the
sheet of FIG. 2A, the coupling projection 15a of the worm shaft 15
is supported from four directions, that is, from both sides in the
longitudinal direction and from both sides in the transverse
direction by the circumferential buffer portions 31 and the radial
buffer portions 32 of the second rubber members 22a, 22b.
[0043] Each of the second rubber members 22a, 22b includes an
engaging portion 34, which extends axially through the worm shaft
coupling portion 26 and is engaged with the coupling portion 26 in
the axial direction. The engaging portions 34 prevent the second
rubber members 22a, 22b from falling off in the axial direction
toward the worm shaft 15.
[0044] Operation of the present embodiment will now be
described.
[0045] When the motor body 2 drives the rotary shaft 8 to rotate,
for example, in the forward direction, that is, clockwise as viewed
in FIG. 2A, the joint 16 rotates together with the rotary shaft 8.
Then, the circumferential buffer portion 31 of the second rubber
member 22a, which contacts the flat surface 15x of the coupling
projection 15a of the worm shaft 15, and the circumferential buffer
portion 31 of the second rubber member 22b, which contacts the flat
surface 15y of the coupling projection 15a, are compressed and
deformed in the circumferential direction by the rotational driving
force of the joint 16, that is, the rotary shaft 8 as shown in FIG.
3. When the load at the output shaft 19 reaches or exceeds a
predetermined value, the contact portions 28b, 28c on the inner
surface of the coupling hole 28 contact the flat surfaces 15x, 15y
of the coupling projection 15a in the circumferential direction,
respectively, so that the rotation of the joint 16 is transmitted
to the coupling projection 15a. This causes the rotary shaft 8, the
joint 16, and the worm shaft 15 to rotate integrally, and the
rotation of the worm shaft 15 is transmitted to the worm wheel 18.
In the rotating state, since the coupling projection 15a of the
worm shaft 15 is contacted and held by the circumferential buffer
portions 31 and the radial buffer portions 32 of the second rubber
members 22a, 22b, the worm shaft 15 is prevented from moving
uncontrollably in directions perpendicular to the axis due to, for
example, imperfect alignment.
[0046] When the load at the output shaft 19 is less than the
predetermined value, the rotation of the joint 16 is transmitted to
the coupling projection 15a of the worm shaft 15 without the
contact portions 28b, 28c on the inner surface of the coupling hole
28 contacting the flat surfaces 15x, 15y of the coupling projection
15a. That is, in this case, the rotation of the joint 16 is
transmitted to the coupling projection 15a via the circumferential
buffer portions 31 of the second rubber members 22a, 22b, so that
the rotary shaft 8, the joint 16, and the worm shaft 15 are rotated
integrally. In this rotating state also, since the coupling
projection 15a of the worm shaft 15 is contacted and held by the
circumferential buffer portions 31 and the radial buffer portions
32 of the second rubber members 22a, 22b, the worm shaft 15 is
prevented from moving uncontrollably in directions perpendicular to
the axis due to, for example, imperfect alignment.
[0047] The motor 1 is configured such that, with the contact
portions 28b, 28c of the coupling hole 28 contacting the flat
surfaces 15x, 15y of the coupling projection 15a, the
circumferential center line L2 of the radial buffer portion 32 of
the second rubber member 22a does not go beyond a corner 35a
defined by the flat surface 15y and the longitudinal-direction end
face 15c of the coupling projection 15a in the forward rotation
direction. The same is the case with the radial buffer portion 32
of the other second rubber member 22b. That is, the motor 1 is
configured such that the circumferential center line L2 of the
radial buffer portion 32 does not go beyond a corner 35b defined by
the flat surface 15x and the longitudinal-direction end face 15d of
the coupling projection 15a in the forward rotation direction. The
corner 35a and the corner 35b are located at symmetrical positions
with respect to the axis L1. The motor 1 is configured to act in
the same manner when the rotary shaft 8 and the joint 16 rotate in
the reverse rotation. Accordingly, when the rotary shaft 8, the
joint 16, and the worm shaft 15 rotate integrally, the radial
buffer portions 32 of the second rubber members 22a, 22b are
prevented from coming off the coupling projection 15a. As a result,
for example, catching of the radial buffer portions 32 by the
coupling projection 15a is prevented, which would be caused if the
radial buffer portions 32 came off the coupling projection 15a.
[0048] As described above, when a state in which the rotary shaft 8
and the speed reduction mechanism 11 are rotating in the forward
direction is switched to, for example, a state in which the load of
the output shaft 19 stops, that is, locks the rotary shaft 8, the
worm portion 15b of the worm shaft 15 and the teeth of the worm
wheel 18 may be bound to each other. If the rotary shaft 8 is
rotated in the reverse rotation in this state, the joint 16 is
rotated in the reverse rotation so that the contact portion 28d of
the coupling hole 28 contacts the flat surface 15y of the coupling
projection 15a, and the contact portion 28e of the coupling hole 28
contacts the flat surface 15x of the coupling projection 15a. By
the time the contact portions 28d, 28e contact the flat surfaces
15y, 15x, the rotary shaft 8 and the joint 16 gain rotational
inertial force. This releases the teeth of the worm shaft 15 and
the teeth the worm wheel 18, which are bound to each other, from
each other in a favorable manner. Likewise, when the rotary shaft 8
is rotated in the forward direction after being stopped while
rotating in the reverse rotation, the teeth of the worm shaft 15
and the teeth the worm wheel 18, which are bound to each other, are
released from each other in a favorable manner. As described above,
according to the present embodiment, the worm shaft 15 is prevented
from moving uncontrollably by the circumferential buffer portions
31 and the radial buffer portions 32 of the second rubber members
22a, 22b, and inertial force of the rotary shaft 8 is ensured by
the circumferential clearances C1 and the radial clearances C2
between the coupling projection 15a and the inner surface of the
coupling hole 28.
[0049] In the present embodiment, due to the characteristics of the
worm shaft 15 and the worm wheel 18, reversal of rotation of the
worm shaft 15 generates a load in the axial direction. At this
time, the load in the axial direction, which acts toward the motor
body 2 and is received by the worm shaft 15, is received by the
projections 21a of the first rubber members 21, which contact the
coupling projection 15a of the worm shaft 15 in the axial
direction. Thus, the first rubber members 21 prevent collision of
the coupling projection 15a against the bottom surface of the
coupling hole 28 in the axial direction, that is, against the end
face 23a of the fixing portion 23 that is close to the worm shaft
15, and collision of the coupling projection 15a against the distal
end 8a of the rotary shaft 8. As a result, the generation of noise
caused by such collisions is prevented.
[0050] The present embodiment has the following advantages.
[0051] (1) The joint 16 is rotational integrally with the rotary
shaft 8. The joint 16 has the coupling hole 28, into which the
coupling projection 15a of the worm shaft 15 is inserted such that
the coupling projection 15a has the circumferential clearances C1
and the radial clearances C2. The circumferential buffer portions
31 and the radial buffer portions 32 are located in the
circumferential clearances C1 and the radial clearances C2 between
the inner surface of the coupling hole 28 and the coupling
projection 15a, respectively. The motor 1 is configured such that,
when the rotary shaft 8 is rotated by the motor body 2, the inner
surface of the coupling hole 28 and the coupling projection 15a
compresses and deforms the circumferential buffer portions 31 in
the circumferential direction, while contacting each other in the
circumferential direction. This reduces uncontrollable movements of
the worm shaft 15 when the motor 1 is operating and stopped. As a
result, the generation of noise caused by the inner surface of the
coupling hole 28 striking the coupling projection 15a is
suppressed. Further, when the rotary shaft 8 is driven to rotate in
the reverse direction with the worm shaft 15 bound with the worm
wheel 18, that is, when the rotary shaft 8 starts rotating in the
reverse direction, the rotary shaft 8 rotates while compressing and
deforming the circumferential buffer portions 31 between the inner
surface of the coupling hole 28 and the coupling projection 15a.
During this time, the inertial force, or the momentum of rotation,
of the rotary shaft 8 is gained. Thereafter, with the
circumferential buffer portions 31 compressed, the inner surface of
the coupling hole 28 and the coupling projection 15a contact each
other in the circumferential direction while receiving the inertial
force of the rotary shaft 8. This releases the teeth of the worm
shaft 15 and the teeth of the worm wheel 18, which have been bound
to each other, from each other. As described above, according to
the present disclosure, the worm shaft 15 is prevented from moving
uncontrollably by the circumferential buffer portions 31 and the
radial buffer portions 32, and inertial force of the rotary shaft 8
is ensured by the circumferential clearances C1 and the radial
clearances C2 between the coupling projection 15a and the inner
surface of the coupling hole 28.
[0052] (2) The rotary shaft 8 and the worm shaft 15 are made of
metal, and the joint 16 is made of plastic and formed separately
from the rotary shaft 8 and the worm shaft 15. Accordingly, the
inner surface of the coupling hole 28, into which the coupling
projection 15a of the worm shaft 15 is inserted, is made of
plastic. Thus, when the motor body 2 rotates the rotary shaft 8,
noise caused by the inner surface of the coupling hole 28 striking
the coupling projection 15a in the circumferential direction is
suppressed. This further suppresses the generation of noise.
[0053] (3) The circumferential buffer portions 31 and the radial
buffer portions 32 are provided in the joint 16, which is a plastic
member separate from the rotary shaft 8 and the worm shaft 15. The
circumferential buffer portions 31 and the radial buffer portions
32 are therefore formed easily.
[0054] (4) Since the circumferential buffer portions 31 and the
radial buffer portions 32 are made of rubber, the worm shaft 15 is
prevented from moving uncontrollably in a favorable manner.
[0055] (5) The first rubber members 21 are located between the
coupling projection 15a and the bottom surface of the coupling hole
28 in the axial direction, that is, the end face 23a of the fixing
portion 23, which is close to the worm shaft 15. Reversal of
rotation of the worm shaft 15 generates a load in the axial
direction. The load may cause the coupling projection 15a of the
worm shaft 15 to strike the end face 23a of the fixing portion 23,
which is close to the worm shaft 15 and the distal end 8a of the
rotary shaft 8. However, such possible striking is suppressed by
the first rubber members 21. As a result, the generation of noise
caused by such striking is suppressed.
[0056] (6) The joint 16, which is a plastic member separate from
the rotary shaft 8 and the worm shaft 15, has the first rubber
members 21. The first rubber members 21 are therefore made
easily.
[0057] (7) Since the first rubber members 21 are made of rubber,
the coupling projection 15ais prevented from striking the bottom
surface of the coupling hole 28 in the axial direction, and the
coupling projection 15a is prevented from striking the distal end
8a of the rotary shaft 8 in the axial direction in a favorable
manner.
[0058] (8) The circumferential buffer portions 31 are located
radially inward of the contact portions 28b, 28c, 28d, 28e on the
inner surface of the coupling hole 28, which contact the coupling
projection 15a. According to this configuration, it is possible to
ensure the space for the circumferential buffer portions 31 while
maintaining the length of the arms for transmitting torque from the
rotary shaft 8 to the worm shaft 15, that is, while maintaining a
long measurement between the axis L1 of the rotary shaft 8 and the
contact portions 28b, 28c, 28d, 28e.
[0059] The embodiments of the present disclosure may be modified as
follows.
[0060] In the above illustrated embodiment, the circumferential
buffer portions 31 and the radial buffer portions 32 of the second
rubber members 22a, 22b are connected to each other by the coupling
portions 33. However, the circumferential buffer portions 31 and
the radial buffer portions 32 may be formed separately from each
other.
[0061] In the above illustrated embodiment, the circumferential
buffer portions 31 and the radial buffer portions 32 of the second
rubber members 22a, 22b are provided in the joint 16. That is, the
circumferential buffer portions 31 and the radial buffer portions
32 are supported by the rotary shaft 8. In a modification, the
circumferential buffer portions 31 and the radial buffer portions
32 may be formed on the flat surfaces 15x, 15y of the coupling
projection 15a of the worm shaft 15. That is, the circumferential
buffer portions 31 and the radial buffer portions 32 may be
supported by the worm shaft 15.
[0062] In the above illustrated embodiment, the first rubber
members 21 are supported by the rotary shaft 8. That is, the first
rubber members 21 are provided on the plastic portion 20 located
about the distal end 8a of the rotary shaft 8. In a modification,
the first rubber members 21 may be supported by the worm shaft 15.
For example, the first rubber members 21 may be formed on an axial
end face of the coupling projection 15a of the worm shaft 15.
[0063] In the above illustrated embodiment, the plastic portion 20
of the joint 16 is fixed to the rotary shaft 8, and the coupling
projection 15a of the worm shaft 15 is inserted into the coupling
hole 28 of the plastic portion 20. However, in a modification, the
relationship may be reversed. That is, the plastic portion 20 may
be fixed to the worm shaft 15, and the distal end 8a of the rotary
shaft 8 may be used as a coupling projection to be inserted into
the coupling hole 28 of the plastic portion 20.
[0064] In the above illustrated embodiment, the joint 16 has the
plastic portion 20, which is separate from the metal rotary shaft
8, and the plastic portion 20 is fixed to the rotary shaft 8. The
embodiment is not limited to this configuration. In a modification,
the joint 16 may be made of the same material as and formed
integrally with the rotary shaft 8. Further, the joint 16, which
functions as a coupling portion, may be provided in the worm shaft
15. The joint 16 may be made of the same material as and formed
integrally with the worm shaft 15.
DESCRIPTION OF THE REFERENCE NUMERALS
[0065] 1 . . . Motor, 2 . . . Motor body, 8 . . . Rotary Shaft, 11
. . . Speed Reduction Mechanism, 15 . . . Worm Shaft, 15a . . .
Coupling Projection, 16 . . . Joint as Coupling Portion, 18 . . .
Worm Wheel, 20 . . . Plastic Portion, 21 . . . First Rubber
Portions (Axial Buffer Portions), 22a, 22b . . . Second Rubber
Portions, 28 . . . Coupling Hole, 31 . . . Circumferential Buffer
Portions, 32 . . . Axial Buffer Portions, C1 . . . Circumferential
Clearances, C2 . . . Radial Clearances.
* * * * *